Title: Ecotoxicological study of fine-recycled aggregate

Abstract

Construction sector is one of the largest consumers of mineral resources, which is also related to the subsequent production of waste. The production of the most widely used products in this sector, such as bricks and concrete, is currently dependent on the constant extraction of primary materials from non-renewable resources. The reuse of recycled materials in the construction industry has considerable potential for saving of the primary resources. Besides the importance of mechanical and chemical features of the materials, it is appropriate to assess the degree of impact on the environment. One option is to perform leaching tests and subsequent ecotoxicity tests with aquatic organisms. In this study, four types of waste construction materials were examined – recycled aggregate (RA) from four different sources. The natural aggregate was examined as well as used as the reference sample. The basic chemical reactions in the view of ecotoxicology were investigated and measured based on both international and Czech standards. Chemical analysis, duckweed growth inhibition test, freshwater algae, and water flea acute toxicity test were performed and discussed. Plant growth and viability of water flea exposed to leachates was compared with both standard growth media and distilled water to determine both toxicity and nutrients lack in the tested samples. Results showed differences among the samples. Masonry-derived aggregate and RA prepared from reinforcement concrete showed no toxicity, while RA originated from highway and ground floor had inhibitory to mild toxic effect. Because of the ecotoxicity observed in selected leachates, landfilling of these materials is not appropriate. A more suitable variant seems to be the use in concrete because of the new assumption that the use of waste materials in concrete leads to their immobilization. This assumption will be verified in a follow-up research.